Yes! And yesOne way to make sense of some of the oddities is this: LE got some sort of tip about RA, be it from KAK or some other source. They got a warrant and searched his house. During the search they found something that definitively ties RA to the crime scene, maybe the clothing items that were mentioned missing in the RL warrant. Maybe something else.
Whatever they found makes them confident they can prove he was at the scene at the time of the crime. But they're not real sure of the scenario beyond that. So they can't rule out the possibility of an accomplice. That means they charge him with felony murder instead of the normal murder charge in case they later find out there was someone else there who did the actual killing. And it means they're cagey about whether he was the guy on the bridge, because they can't prove that for sure (hence no separate kidnapping charge and no charge for tampering with the bodies). And it means they keep asking for tips, because there's still a lot they don't know about how it went down.
My only problem with that scenario is that it makes the arrest seem a bit premature. You'd think they'd wait to flesh out the case before they arrested RA. But perhaps they were worried that the search had tipped him off and decided they needed to get him in custody.